Android4.0 以后不允许在主线程进行网络连接

Android4.0 以后不允许在主线程进行网络连接，否则会出现 android.os.NetworkOnMainThreadException。因此，必须另起一个线程进行网络连接方面的操作。

package com.lujinhong.irmcdc.dao; import java.io.IOException; import java.net.Socket; import java.net.UnknownHostException; import java.util.Scanner; public class ResourceDao { String returnLine = "hi"; public String getAllContentByName() { Runnable r = new NetWorkHandler(); Thread thread = new Thread(r); thread.start(); try { Thread.sleep(15000); } catch (InterruptedException e) { e.printStackTrace(); } return returnLine; } private class NetWorkHandler implements Runnable { String line = "line"; Socket socket = null; Scanner scanner = null; @Override public void run() { try { socket = new Socket("time-A.timefreq.bldrdoc.gov", 13); scanner = new Scanner(socket.getInputStream()); while (scanner.hasNextLine()) { line = scanner.nextLine(); returnLine += line; } } catch (UnknownHostException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } finally { scanner.close(); try { socket.close(); } catch (IOException e) { e.printStackTrace(); } } } } }

1、由于网络连接需要一定时间，为了在主界面上进行网络信息的展现，暂时用sleep()方法简单实现，使主线程等待网络信息读取完成。

Thread.sleep(5000);

修改以下 问题，使用wai()及nofifyAll处理。

package com.ljh.irmcdc.dao; import java.io.IOException; import java.net.Socket; import java.net.UnknownHostException; import java.util.Scanner; public class ResourceDao { String returnLine = ""; public String getAllContentByName() { Runnable r = new NetWorkHandler(); Thread thread = new Thread(r); thread.start(); synchronized (this) { try { wait(20000); } catch (InterruptedException e) { e.printStackTrace(); } } return returnLine; } private class NetWorkHandler implements Runnable { String line = "line"; Socket socket = null; Scanner scanner = null; @Override public void run() { try { // socket = new Socket("time-A.timefreq.bldrdoc.gov", 13); socket = new Socket("192.168.136.44", 8179); scanner = new Scanner(socket.getInputStream()); returnLine = ""; while (scanner.hasNextLine()) { line = scanner.nextLine(); returnLine += line; } //不要直接使用this，否则nofity的对象不是上面wait所锁定的对象。 synchronized (ResourceDao.this) { ResourceDao.this.notifyAll(); } } catch (UnknownHostException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } finally { scanner.close(); try { socket.close(); } catch (IOException e) { e.printStackTrace(); } } } } } 注意：

1、在内部类中引用外部类对象的方法：

ResourceDao.this.notifyAll(); 2、wai()及nofity()必须放在synchronized块里面。

尤其注意在内部类中notify()外部类对象时，不要使用this，而应该是上述所表。

转载于:https://www.cnblogs.com/jinhong-lu/p/4559520.html